Hemodialysis is used for removing toxic wastes from the human body in cases of renal failure. The patient's blood is temporarily brought outside of the body via tubes and passed through at least one semi-permeable membrane, which may be a group of hollow fibers, in a dialyzer. The semi-permeable membrane separates the blood from a dialysate solution. Impurities from the blood pass through the membrane and into the dialysate solutions, primarily by osmotic pressure. The cleansed blood is then returned to the body.
Standard dialysis treatment, using an installed apparatus in hospitals, comprises two phases, namely, (a) dialysis, in which toxic substances and scoriae (normally small molecules) pass through the semi-permeable membrane from the blood to the dialysis liquid, and (b) ultrafiltration, in which a pressure difference between the blood circuit and the dialysate circuit, more precisely a reduced pressure in the latter circuit, causes the blood content of water to be reduced by a predetermined amount.
Dialysis procedures using standard equipment tend to be cumbersome as well as costly, besides requiring the patient to be bound to a dialysis center for long durations. Conventional systems are also less reliable because of the necessity of using a myriad of tubes comprising the fluid circuits of the purification systems, thus increasing the risks of leakage and breakage. Accordingly there is need in the art for an extracorporeal blood processing system that can be operated in hemodialysis as well as hemofiltration modes, while at the same time offering reasonable portability to the patient. Such a portable dialysis system should also be conducive to using disposable components. Further, there is also a need for novel manifolds for dialysis systems with integrated blood purification system components, such as sensors, pumps and disposables, as well as molded blood and dialysate flow paths to avoid a complicated mesh of tubing and to enhance the robustness of the system.
Conventional sorbent-based dialysis systems require the blood side of the disposable dialysis circuit to be primed with sterile saline before each treatment prior to allowing the patient's blood to enter the circuit. This is an important first step to purge the system of any air. In operation, the patient's blood enters tubing filled with the saline solution and “chases” the saline solution to waste, after which dialysis begins. U.S. Pat. No. 4,661,246 describes a typical single access dialysis instrument having a single catheter for receiving body liquids, a dialyzer having a body liquid side with fluid inlet and fluid outlet connected to the catheter and further having a dialysate side with a dialysate inlet and a dialysate outlet. The dialysis instrument described also includes storage means for holding a supply of liquid, including dialysate for use in the dialyzer.
US Patent application No. 20020017489 and U.S. Pat. No. 6,187,198 describe systems and methods of priming a blood processing circuit in which both the retention of undesirable air bubbles and the risk of contamination is reduced.
US Patent application No. 20020017489 provides an arterial set and a venous set for blood flow between a blood processing unit and a patient. Each set has a main tube which carries a chamber in in-line flow relationship, and a branch tube extending from the chamber to empty into a drain receptacle. A portion of the branch tube extends through an upper wall of the chamber and projects for a distance into the chamber to spontaneously create an air bubble of desired operating volume above a liquid level in the chamber. The patent application describes a method of priming by passing a priming solution in a first direction of flow through at least one of the sets, to cause the priming solution to enter an in-line chamber carried by the one set in a flow direction that is retrograde to the normal direction of blood flow through the chamber. Next, the steps of removing air from the one set through a port and passing the priming solution in a reverse direction of flow to the first direction are performed preferably simultaneously in order to complete priming of the blood processing unit.
US Patent Application 20070185430 provides a system and method for producing purified replacement fluid in a unit used for renal replacement therapy on a patient. The system can be used both to purify non-purified fluid and to further purify sterile fluid contaminated (e.g., by touch contamination) during connection. The method employs the use of a filter with a membrane, having a pore size smaller than the non-purified and pyrogenic material to be filtered, separating a waste side of the filter from a clean side, and a pump in fluid communication with a container of a replacement fluid in fluid communication with the waste side of the filter, and a second container for holding purified replacement fluid in fluid communication with the clean side of the filter. The pump switches between a first direction that pumps fluid out of the first container and a second direction that removes waste from blood.
All of the above mentioned patents and patent applications describe various dialysis circuits and priming methods and are incorporated herein by reference.
Conventionally, the priming procedure requires a minimum of a liter of priming fluid such as saline, a clamp, tubing, connectors and a pole from which to hang the bag. A patient, or healthcare provider, must connect the line, open the clamp, close the clamp and dispose of the waste. This is a problem because a) it requires a high skill level to set up and manage the priming procedure and b) it requires extra materials. It would be preferred to use a more convenient priming fluid source and to simplify the priming procedure such that trained health care professionals are not required to manage and/or handle the priming process.